A, E, F, H, I, L, M, N, O, __, __

The next two letters in the series are R and S.

EXPLANATION:

The sequence is constituted by letters whose pronounciations start with a vowel sound.

Consequently, the next two letters in the series are R and S, and the complete sequence is:

A, E, F, H, I, L, M, N, O, R, S, U, X